Back in Jan. 2014, following the long stormy weather, I noticed that the felt along the 2 valleys (felt on the edge of the valley rafter) in the loft is wet. Our neighbour recommended a roofer who had a look and said the rain got in via the cracks in mortar (he said the cracks are inevitable due to movement etc.) in severe weathers. The felt is ok. From outside the fiberglass valley looks ok too. He asked me to wait until summer and contact him again so he can apply some sort of (flexible) sealant to seal the cracks.

I have been monitoring it for the past 5 months, especially after heavy rains. The felt has been dry. So it seems rain only get through from the cracks in extreme weathers (e.g. rain driven by strong winds). Do you think sealing the valley (per the roofer's advice) would help or I can just leave it for now as severe weather like we had last winter is rare (since under normal weather the felt is dry)?

Hi, if it leaked once it will not get better on it's own I'm afraid. If there are cracks in any kind of masonry or mortar water onbiously gets in. If there is a cold snap, this water can freeze. When it freezes it expands into ice which makes the crack a tiny bit bigger letting more water in and so on...........This is called Freeze-Thaw action and you can read more about it here http://www.diydoctor.org.uk/projects/Freezethaw.htm Our advice would be to get it repaired while there is no damage as its easy to forget about these things nd before you know it you have a full-scale leak.

Good luck and please do let us know how you get on, it may help othes.

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